At least two of the A4-sized jiffy bags sent to the locations had Irish postage stamps attached to, reports The Mirror Online .

One also included a return address in the Republic of Ireland.

Photographs of the stamps appear to resemble a 'Love & Marriage stamp' which are available in Irish post offices and were issued in 2018 to celebrate Saint Valentine's Day.

According to reports, detectives in Ireland are now investigating whether the three incidents - which have been linked by the Met - may be linked to dissident republican groups operating in Northern Ireland.